Chemistry: electrical and wave energy – Processes and products – Processes of treating materials by wave energy
Patent
1998-08-27
2000-07-25
Gorgos, Kathryn
Chemistry: electrical and wave energy
Processes and products
Processes of treating materials by wave energy
20415715, 20415746, 20415749, 2041582, 588227, 588243, 588247, 588900, 2504923, 422186, 42218604, B01D 5300, C07C 100, C01B 2100, B09B 300, A61N 500
Patent
active
060932880
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a desulfurizing process and apparatus by irradiation of electron beam, and more particularly to a process and an apparatus for desulfurization by injection of ammonia into a high temperature gas containing sulfur oxides such as a combustion flue gas discharged from a boiler and irradiation of electron beam.
BACKGROUND ART
As economy develops, more and more energy is demanded. Amidst the continuous growth of energy demand, energy source is still dependent on fossil fuels such as coal and petroleum. However, the harmful products or pollutants generated by the burning of fossil fuels are responsible for global pollution. To prevent the release of pollutants into the atmosphere and to stop the pollution of global environment, development work is being carried out at an accelerated pace to create a flue gas treatment system for installation in fuel combustion plant such as thermal power plants. There are still many areas of improvement to meet problems such as the complicated configuration of the equipment requiring a large number of control variables and the need for large-scale waste water treatment systems requiring sophisticated treatment technology.
In an effort to solve these problems, a flue gas treatment system in which flue gas discharged from the fuel combustion facility such as a boiler is treated by irradiation of electron beam has been developed.
In this system, ammonia is injected into a high temperature gas containing sulfur oxides, and the mixed gas is irradiated with electron beam to remove the sulfur oxides therefrom in the form of a powder of ammonium compounds. In this case, the lower the temperature of gas is, the higher the reaction rate between sulfur oxides and ammonia is. Therefore, the high temperature gas is required to be cooled to a certain range of temperature. Accordingly, conventionally, the gas is normally cooled to a temperature ranging from an adiabatic saturation temperature plus 10.degree. C. to 80.degree. C. by water spray at the top of a cooling tower which is located in the system upstream of a process vessel in which ammonia is injected. The cooling tower is a complete evaporating type in which the sprayed water is completely evaporated. The gas cooling system has such an advantage that no waste water treatment system is required to be installed because of generation of no waste water. Further, by controlling the amount of sprayed water, the temperature of gas discharged from the cooling tower can be adjusted.
However, if the concentration of sulfur oxides is relatively large and/or the dose of electron beam is relatively large, an increase of the gas temperature caused by the heat of reaction between sulfur oxides and ammonia and/or by the heat generation due to irradiation of electron beam is not negligible. Therefore, in order to avoid lowering the reaction rate due to an increase of the gas temperature, after cooling of the gas in the cooling tower, it is necessary to adjust the gas temperature in the range of 50 to 80.degree. C. by water spray in a process vessel. At this time, the sprayed water is completely evaporated in the process vessel or in the subsequent stage, and hence waste water is not generated in the process vessel as well (hereinafter suppression of an increase of the gas temperature by evaporation of sprayed water in the process vessel is referred to as "secondary gas cooling", and the cooling of the gas before the reaction step is referred to as "primary gas cooling").
FIG. 3 is a schematic view of a conventional electron beam flue gas treatment system. As shown in FIG. 3, flue gas containing sulfur oxides discharged from a boiler 1 which is a kind of fuel combustion facility is cooled in a heat exchanger 2, and then introduced into a cooling tower 4. In the cooling tower 4, water supplied from a pump 3 is sprayed by a single-fluid nozzle 6, and the sprayed water is completely evaporated therein. The cooling tower 4 is a complete evaporating type in which the sprayed water is completely evaporated
REFERENCES:
patent: 4882020 (1989-11-01), Maezawa et al.
patent: 5244552 (1993-09-01), Namba et al.
patent: 5834722 (1998-11-01), Tokunaga et al.
Iizuka Yoshitaka
Izutsu Masahiro
Ebara Corporation
Gorgos Kathryn
Wong Edna
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